b8ae2f24af
Switching to save_layer_utils regressed perf/memory usage on several devicelab benchmarks, see https://flutter-flutter-perf.skia.org/e/?queries=device_type%3DPixel_7_Pro%26sub_result%3D90th_percentile_gpu_memory_mb%26sub_result%3Daverage_gpu_memory_mb%26test%3Dnew_gallery_impeller_old_zoom__transition_perf&selected=commit%3D42418%26name%3D%252Carch%253Dintel%252Cbranch%253Dmaster%252Cconfig%253Ddefault%252Cdevice_type%253DPixel_7_Pro%252Cdevice_version%253Dnone%252Chost_type%253Dlinux%252Csub_result%253D90th_percentile_gpu_memory_mb%252Ctest%253Dnew_gallery_impeller_old_zoom__transition_perf%252C The reason is that the source_coverage_limit [intersection](https://github.com/flutter/engine/blob/main/impeller/entity/save_layer_utils.cc#L67-L68) is highly unstable from frame to frame if there is an animated blur and/or image filter. This change mostly matches the old entity pass behavior. . In cases where the difference between the intersected coverage result is small (< 20% in both dimensions), we just use the transformed content coverage. The old behavior would _always_ use the transformed content coverage even if it was substantially large than the coverage limit. This posed problems if folks drew content larger than the max texture size. This herustic attempts to prevent that by allowing the source coverage limit to kick in once the difference is larger than 20% in either direction